KVM: x86: fix missing checks in syscall emulation

[pandora-kernel.git] / arch / x86 / kvm / emulate.c

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index f1e3be1..f5302da 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1877,6 +1877,51 @@ setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
        ss->p = 1;
 }
 
+static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)
+{
+       struct x86_emulate_ops *ops = ctxt->ops;
+       u32 eax, ebx, ecx, edx;
+
+       /*
+        * syscall should always be enabled in longmode - so only become
+        * vendor specific (cpuid) if other modes are active...
+        */
+       if (ctxt->mode == X86EMUL_MODE_PROT64)
+               return true;
+
+       eax = 0x00000000;
+       ecx = 0x00000000;
+       if (ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx)) {
+               /*
+                * Intel ("GenuineIntel")
+                * remark: Intel CPUs only support "syscall" in 64bit
+                * longmode. Also an 64bit guest with a
+                * 32bit compat-app running will #UD !! While this
+                * behaviour can be fixed (by emulating) into AMD
+                * response - CPUs of AMD can't behave like Intel.
+                */
+               if (ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx &&
+                   ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx &&
+                   edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx)
+                       return false;
+
+               /* AMD ("AuthenticAMD") */
+               if (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx &&
+                   ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx &&
+                   edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx)
+                       return true;
+
+               /* AMD ("AMDisbetter!") */
+               if (ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx &&
+                   ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx &&
+                   edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx)
+                       return true;
+       }
+
+       /* default: (not Intel, not AMD), apply Intel's stricter rules... */
+       return false;
+}
+
 static int em_syscall(struct x86_emulate_ctxt *ctxt)
 {
        struct x86_emulate_ops *ops = ctxt->ops;
@@ -1890,9 +1935,15 @@ static int em_syscall(struct x86_emulate_ctxt *ctxt)
            ctxt->mode == X86EMUL_MODE_VM86)
                return emulate_ud(ctxt);
 
+       if (!(em_syscall_is_enabled(ctxt)))
+               return emulate_ud(ctxt);
+
        ops->get_msr(ctxt, MSR_EFER, &efer);
        setup_syscalls_segments(ctxt, &cs, &ss);
 
+       if (!(efer & EFER_SCE))
+               return emulate_ud(ctxt);
+
        ops->get_msr(ctxt, MSR_STAR, &msr_data);
        msr_data >>= 32;
        cs_sel = (u16)(msr_data & 0xfffc);